A known air/oil separator comprises a rotor, which has an inlet at a first axial end for the supply of an air and oil mixture into the air/oil separator and the rotor has an outlet at a second axial end for discharging cleaned from the air/oil separator. The rotor carries an annular porous member. The air and oil mixture flows axially through the porous member and oil is centrifuged radially outwardly from the porous member and the air flows radially inwardly to subsequently flow axially out of the air/oil separator. This arrangement is shown in our UK patent GB1508212.
A further known air/oil separator is similar to the previously mentioned one, but the air outlet is also at the first axial end of the air/oil separator. The air and oil mixture axially through the porous member and oil is centrifuged radially outwardly from the porous member and the air flows radially inwardly to subsequently flow axially out of the air/oil separator. This arrangement is shown in U.S. Pat. No. 5,716,423 and U.S. Pat. No. 6,033,450.
However, it has been found that there is still some oil discharged from the air/oil separator with the air. This leads to the undesirable emission of oil from the gas turbine engine, staining of the outer surface of the fan casing and increasing the oil consumption of the gas turbine engine.